Battery charging device

ABSTRACT

A battery charging device comprising in combination: A TRANSFORMER FOR TRANSFORMING AN AC power line supply into usuable energy; a pulsating charging circuit operatively coupled to said transformer and disposed for charging a battery across a charging terminal (18) supplying a pulsating charging current during each half cycle of AC alternation; sensing circuit means connected to said charging terminal for sensing the voltage charged in said battery during the non-charging 1/2 cycle; a measurement and memory circuit connected to said charging circuit and said sensing circuit means including storage means for storing a charge therein which is a function of said battery charge; and, control means responsive to said voltage sensing and coupled to said charging circuit for changing the rate of charge for a time period measured by said measurement and control circuit.

United States Patent 1 Saslow [4 1 May 15, 1973 54] BATTERY CHARGINGDEVICE 3,531,706 9 1970 Mullersman ..320 39 x 75 [n tr: Se 0rSl0,S t S'Ven o N u as w ara Oga prmgs Primary ExaminerJ. D. M11ler AssistantExaminer-Robert J. Hickey [73] Assignee: Espey Mfg. & Electronics Corp.,A ttorney-George B. Oujevolk Saratoga Springs, N.Y. 22 Filed: Aug. 25,1971 [57] ABSTRACT [21] AppL No: 174,611 A battery charging devicecomprising in combination:

a transformer for transforming an AC power line supply into usuableenergy; a pulsating charging cir- [52] U.S. Cl. 320/44 uit operativelycoupled to Said transformer and [51] Int. Cl ..H02j 7/04 di posed forcharging a battery across a charging ter- Fleld of Search 40, 35, 44,mina] a pulsating charging current dur- 23 ing each half cycle of ACalternation; sensing circuit means connected to said charging terminalfor sensing [56] References Cited the voltage charged in said batteryduring the noncharging /z cycle; a measurement and memory circuit UNITEDSTATES PATENTS connected to said charging circuit and said sensing cir-3,178,629 4/1965 Saslow ..320 23 Quit means including Storage means forstoring a 3,356,922 12/1967 Johnston ..320/40 X charge therein which isa function of said battery 3,409,815 11/1968 Wright et al..........320/37 X charge; and, control means responsive to said voltage3,443,239 6/1969 i r X sensing and coupled to said charging circuit forchang- 3,564,382 9/1968 Kmg et 320/39 ing the rate of charge for a timeperiod measured by 3,421,066 l/1969 Flynn et a] ..320/23 X Saidmeasurement and control circuit 3,329,882 7/1967 Sobel ..320/DIG. l

4 Claims, 6 Drawing Figures CHA G INTERNAL POWER SUPPLY 1 22 cmcusrs I ITR'CKLE CHARGE INDICATOR OVERCHARGE CHARGE CHARGE I4 I MEASUREMENT LAMPINTERVAL 28 AND MEMORY ClRCUlT CIRCUIT BATTERY BEING VOLTAGE SENSINGcmcun' CHARGED PATENTED I 51973 SHEET 2 BF 6 IN VENTOR.

BY H

BATTERY CHARGING DEVICE BACKGROUND OF THE INVENTION .The presentinvention relates to battery chargers, and more particularly to abattery charger for nickel cadmium batteries.

BRIEF DESCRIPTION OF THE PRIOR ART The use of devices, so calledcordless, which employ sealed nickel cadmium battery means for theirpower source have usually employed the technique of float charging orover night charging. These nickel cadmium batteries have foundapplication in electric tooth brushes, shavers, power tools, etc. Therehave been attempts at fast charging of sealed nickel cadmium batteries,however, as yet there is no system which has been widely adapted or ispractical and reliable. The problems encountered in charging sealedcells are somewhat similar to the charging of vented cells, but withcertain exceptions.

It is the concensus of opinion that a charge schedule for sealed cellsshould be one where 1 percent of the energy removed from the cell isreplaced, as compared to 150 percent for vented cells. The presentinvention is directed to a fast charging system which puts a charge andovercharge on the battery as a function of its past discharge cycle.

SUMMARY OF THE INVENTION Generally speaking, the system contemplatedherein employs half-wave charging. A silicon controlled rectifier isused here in this mode. In the off portion of the cycle the battery isinterrogated for its open circuit voltage, while in the other half cycleenergy is fed into the battery at a high rate. For example, if theparticular system uses 2 one ampere hour batteries, the average chargingcurrent is 5 amperes with approximately amperes peak. During the offportion of the cycle, while monitoring the open circuit portion, theapparatus looks for the rise of battery terminal EMF. This is done by avoltage sensing means. While the battery is being charged a timingcapacitor is receiving a charge which is proportional to the energydelivered to the battery. When the voltage sensing means tells theapparatus that the battery has reached the 90 percent charge point, thecharge to the timing capacitor is arrested and the control of theremaining portion of the charge cycle is maintained as a function of thecharge retained on the timing capacitor.

During the main charge the timing capacitor is charged up to the battery0.9C point and then it is allowed to discharge so that l.lC is put intothe battery. For economy and speed of charge the overcharge rate remainsthe same as the charge rate. From a practical standpoint there is nosignificant heating of the battery. Repeated cyclical operationdeploying this schedule shows on testing that the battery maintains itsrated capacity. A diode/resistor network across the SCR provides a floatmeans at a small fraction, about l/th of the initial charge rate.

The invention, as well as other object and advantages thereof willbecome more apparent from the following detailed description when takentogether with the accompanying drawings, in which:

FIG. 1 is a block diagram of a battery charging system contemplatedherein;

FIG. 2 shows schematically some of the components of the block diagramof FIG. 1;

FIG. 3 schematically illustrates other components of the block diagramof FIG. 1;

FIG. 4 is a schematic embodiment of the inventive concept shown in FIG.1;

FIG. 5 is a block diagram of a second embodiment according to theinventive concept; and,

FIG. 6 shows a schematic drawing of FIG. 5.

The device shown in block diagram in FIG. 1 is a pulse-type constantcurrent battery charger, primarily used for recharging nickel-cadmiumtype secondary cells or batteries. Its use is not restricted tonickelcadmium batteries, however. The important features of the deviceshown in FIG. 1 are in the circuits, and their use, that allows anactual measurement of the charge current and charge time required tobring a battery to percent of its full charge capacity. This 90 percentpoint is normally the potential or voltage point where other chargesystems cease charging. The device 10 shown in FIG. 1 includes chargingcircuits 12 having a trickle charge circuit 14 and a main chargingcircuit 16, both connected over an output terminal 18 to a battery 20.These charging circuits 12 are connected to an internal power supply 22and the battery is also coupled to a voltage sensing circuit 24. Thevoltage sensing circuit 24 is connected to a charge measurement andmemory 26 and to an overcharge interval circuit 28. These circuits, inturn, are connected to an indicator lamp circuit 30. The device 10stores in the charge measurement and memory circuit 26 the total chargecurrent value and total charge time value. When the 90 percent chargepoint is reached, as measured in the voltage sensing circuit 24, thecharge measurement and memory circuit is activated and the main charge16 is continued for approximately 20 percent of the original chargetime. This insures that the battery accepts percent recharge and not thenormal 90 percent recharge.

To facilitate the understanding of the invention, some of the particularcircuits illustrated in the block diagram are in some cases shownseparately. Thus, the main charging circuit is shown in FIG. 2

THE MAIN CHARGING CIRCUIT This circuit has a step-down isolation firstsecondary ofa transformer 32, with end points H and J, connected on theone side in series to a main charging SCR 34 in series with the battery20 being charged, and on the other side to a current limiting resistor36. The control electrode of the charging SCR 34 is in turn controlledby the emitter electrode of NPN transistor 38 whose base is controlledby the collector electrode of NPN transistor 40. Associated with controltransistor 38 are collector resistor 42 and base bias resistor 44. Theemitter of transistor 40 is in turn connected midpoint between a line ofdiodes 46, 47, 48, 49, which provide a voltage reference.

In parallel with main charging SCR 34 is the trickle charge circuit 14consisting of diode 50 and resistor 52 which are also in series withbattery under charge 20. In parallel with current limiting resistor 36is the input to the indicator lamp, namely, NPN transistor 54 andresistor 56, connected to the transistor emitter. The transistor 54collector electrode is connected to the indicator lamp circuit.

The main charging SCR 34 supplies half wave charging current to thebattery 20 when the transformer 32 terminals H and J are positive. It isgated on by transistor 38 through diode 39. The control transistor forthis circuit is transistor 40.

When the main charging SCR 34 is biased off, the trickle current flowsthrough diode 50 and resistor 52. The value of resistor 52 determinesthe trickle curren value.

INTERNAL POWER SUPPLY Internal power for the unit is supplied across asecond secondary 58 with diodes 60 and 62. The output side of diode 60is in series with the collector electrode of NPN control transistor 38,and the input side is in series with one end of second secondary 58. Inparallel with diode 60 is another diode 64 and a capacitor 66 connectedto ground. The back-to-back diodes provide power for the controltransistor 38. Diode 62 is connected to a tap 62a on the secondtransformer secondary 58 and supplies the necessary voltage forreference diodes 46, 47, 48, 49 and is in series with these diode biasresistors 68, 70 in parallel with power diode 62 and capacitor 72 inparallel with the output to the reference diodes complete this sectionof the power circuit. Another output side of the power circuit is to ahexinverter across filter capacitor 74.

The internal power is supplied from half wave rectification by diode 64.It is filtered by capacitor 66. The other half wave rectifier circuitconsists of diode 62 and capacitor 72. The voltage reference consists ofdiodes 46, 47, 48 and 49.

For three of the blocks shown in FIG. 1, namely blocks 24, 26 and 28,that is to say, the voltage sensing circuit, the charge measurement andmemory circuit and the overcharge interval circuit, use is made of ahexinverter 76. This hexinverter is shown in FIGS. 3 and 4 and is anintegrated circuit chip having six amplifiers therein, A through F.However, use of the hexinverter is only for convenience, since theseunits are commercially available and are easily connected to perform therequired functions. The hexinverter, though of course an extremelyuseful component, is not essential to the present invention, since thesame function can be performed by the use of individual amplifiers.Therefore, although the hexinverter 76 is indicated as being one singleunit, for the purpose of understanding the present inventive concept, itis best to disregard the dash-line box around this component and totreat the individual units as if they were not part of an integratedcircuit chip. However, since the voltage sensing circuit 24, the chargemeasurement and memory circuit 26 and the overcharge interval circuit 28all use the hexinverter 76, these three circuits are shown on onedrawing figure, namely FIG. 3.

THE VOLTAGE SENSING CIRCUIT For this circuit, use is made of hexinverter76, sections A, B and F. As hereinbefore mentioned, the device chargesfor 1% cycle and then measures for l cycle.

The battery under charge 20 is connected to the charging circuits 12across an output terminal 18. Connected to the output terminal 18 is aresistor bridge 78 consisting of resistors 80, 82, 84, 86, and variableresistor 88. These resistors are connected to terminal 18 by a line 90.Resistors 80 and 82 are in parallel with the battery and in seriesacross the base of an NPN transistor 92. Resistors 84 and 86 are inparallel with the battery and resistors and 82. Resistors 84 and 86which are in series with each other across variable resistor 88 form avoltage divider. Variable resistor 88 has an adjustable center tap 94which connects to amplifier A of hexinverter 76. Amplifier A is inseries with amplifier B, which in turn is in series with a voltagesensing resistor 96 across a diode 98. Capacitors 100 and 102 areelectrical, noise supression devices, allowing the device to operatesatisfactorily in electrically noisy" environments. Power from the tapof the internal power supply second secondary 58 passes across a supplyline 104 to amplifier F of the hexinverter 76 and the output fromamplifier F is connected to the output of amplifier B in parallel withstorage capacitor 106.

During the non-charging half-cycle, voltage sensing is accomplished bythe parallel output connections of hexinverter 76, sections B and F.I-Iexinverter section A measures the battery voltage through voltagedivider resistors 84, 86, and 88. This occurs during both charging andnon-charging half-cycles. Hexinverter section B inverts the output ofsection A. During the charging half-cycle the output of hexinverter 76,section F is low; this clamps the output of section B to ground. Duringthe non-charging half-cycle the output from hexinverter section F ishigh. When the battery voltage is above its 0.9C value and thenon-charging interval occurs at the same time there is a high outputsignal available at junction point K. This is the junction point betweensection B, section F and diode 98. This signal is inverted to low byhexinverter section C, disables the charge measuring circuit, andterminates the main charge.

MEASUREMENT AND MEMORY CIRCUIT The charge measurement and memory circuit26 includes hexinverter 76 section C, NPN transistors 108 and 110,resistors 112, 114, 118 and PNP transistor 110, diode 120 and memorycapacitor 122, transistor 108 has its base connected to the output ofsection C across resistor 114 to which it is connected at a junctionpoint L. From junction point L, resistor 1 12 is connected to ground.The collector of transistor 108 is in series with the base of transistorand also in series with diode 120, resistors 118 and 116. One end ofresistor 116 is connected to the emitter of transistor 110, whereas theother end is connected to a junction point M where it is joined toresistor 118.

The charge measurement circuit is controlled by section C of thehexinverter 76. During the battery charging intervals, transistor 108 isbiased on by secti" .1 C of hexinverter 76. The collector current oftransistor 108 is the tum-on base current for transistor 110. Thecollector current of transistor 1 10, at a rate determined by resistor l16 is the input to memory capacitor 122 of the charging current. Thecharge, received by memory capacitor 122 is directly proportional to thecharge received by the battery. Memory capacitor 122 is connected on oneside to the collector electrode of transistor 110 at junction points Nand P and on the other side to the indicator lamp circuit 30 across NPNtransistor 116a, the overcharge interval circuit 28 and to the internalpower supply 22 at a junction point Q.

OVERCHARGE INTERVAL CIRCUIT The charge interval is measured for the timerequired to bring the battery to the 90 percent or 0.9C condition. Thischarge interval information is stored in the memory circuit. The maincharge is terminated at this 90 percent or 0.9C point and the overchargeinterval begins.

It has been determined that the additional energy required to charge anickel-cadmium battery from its 0.9C status to its charged statusamounts to approximately percent of of the energy that was required tocharge the battery from its original state of charge to its 0.9C status.

The overcharge interval circuit extends the main charge for a timeconsistent with the value recorded in the memory. At the completion ofthe overcharge interval the main charge circuit is turned off, thetrickle charge begins, and the charge complete indicator lamp lights.

The .overcharge interval circuit 28 generally includes hexinverter 76,section D, NPN transistor 124, differential amplifier 126 and resistors128, 130, 132, 134, and diodes 136 and 138 which link the voltagesensing circuit 24 to the overcharge interval circuit 28. Section D isconnected on the output side to the base of NPN transistor 124 and theoutput side is also in series with diode 138 connected to junction pointX of the voltage sensing circuit and to the collector of voltage sensingNPN transistor 92. Resistors 128 and 130 are in parallel to the plusinput of differential amplifier 126 and resistor 132 is connected to theminus input of this differential amplifier. The output side of thedifferential amplifier 132 is connected across resistor 134 and on theone hand goes across diode 136 and on the other hand goes to the base ofcontrol transistor 40. Resistors 128, 130, and 132 on the outer side arerespectively connected as follows: 128 is connected to power diode 62and to the indicator lamp circuit resistor 130 is connected to junctionpoint Q; and, resistor 132 is connected to junction points P and N.Thus, one resistor 130 is connected on one side of memory capacitor 122,while the other resistor 132 is connected to the other side of thememory capacitor.

The overcharge interval is started by a high output signal from sectionD of the hexinverter 76. It is terminated by the threshold switchingvoltage of differential amplifier 126. A high signal from hexinverter 76turns on transistor 124. The simultaneous low signal from hexinverter 76section C turns off transistor 108 disassembling the memory chargecircuit. The collector current of NPN transistor 124 through resistor141 is the memory discharge current. When the decaying voltage acrossmemory capacitor 122 passes the threshold switching voltage ofdifferential amplifier 126 the output of the differential amplifier 126switches from low to high.

INDICATOR LAMP CIRCUIT The indicator lamp circuit includes a lamp 140,NPN transistors 54, 144, 146, capacitor 148, and resistors 150, 152,154, 156, 158. The lamp 140 is connected to the collector of transistor146. The emitter of transistor 146 is connected to the collector oftransistor 144 and the base of transistor 144 is connected to theemitter of transistor 54. As heretofore mentioned, transistor 54 is theinput to the indicator lamp. Resistor 150 provides a load for the lamp.Resistors 152 and 154 are the base bias resistors for transistor 146.Resistor 156 is the base bias resistor for transistor 144, whileresistor 158 provides a load bias for transistor 54.

The ready lamp is powered through transistor 146. The control transistor144 is clamped in its off condition by transistor 54 when chargingcurrent is flowing. Transistor 144 turns on during the charging halfcycle when the main charge SCR 34 is turned off. Capacitor 148 insuresthat the lamp stays on for both half cycles of the line supply voltage.

Upon connection to a 1 l5v/6O Hz power source and insertion of a twocell nickel-cadmium battery, the supply begins to function. The supplyfirst measures the battery terminal voltage to determine if a charge isrequired. If the battery voltage indicates a charged battery thefunction control circuits inhibit the main charging circuits, allow atrickle charge and energize the charge complete indicator lamp. If thebattery requires a charge then the main charge circuits are allowed tofunction.

A simpler version of the device shown in FIG. 1 is shown in FIG. 5. Herethe charging circuits 12a are connected to battery 20a by terminal 18a.The voltage sensing circuit 24a is also connected to the battery, whilethe measurement and memory circuit 20a is connected to the voltagesensing circuit 24a and to the charging circuits 12a. These circuits inturn are controlled by a control circuit 25.

CHARGING CIRCUIT The basic charging circuit shown in FIG. 6 consists ofa step-down isolation transformer 202, a current limiting resistor 204and a silicon controlled rectifier (SCR) 206. The secondary low voltagewinding of transformer 202 is connected in a series circuit with currentlimiting resistor 204 and SCR 206 and the battery under charge 20a.

During the secondary voltage half wave interval, point A of thetransformer is positive with respect to B. Current which is limited byresistor 204 flows from point A through resistor 204 and SCR 206, ifturned on, into the positive terminal of the battery 20a. The returnpath of this charging current is across the battery 20a to terminal B ofthe transformer 202.

During the secondary voltage half wave interval, when point A oftransformer 202 is negative with respect to point B, no charging currentflows. This is because SCR 206 is reverse-biased and presents an opencircuit. Also, when point A is positive and SCR 206 is not turned on byits control circuits, no charging current will flow.

THE VOLTAGE SENSING CIRCUIT The voltage sensing circuit consists ofresistor 208, diodes 210, 212, NPN transistor 214, resistor 216,resistor 218, capacitor 220 and winding terminals B and C of transformersecondary 202. Resistor 208 and diodes 210, 212 are in series withterminal C. These bias the base of transistor 214 coupled to the base ofN PN transistor 215 by its collector. Resistor 216 provides bias betweenthe collector of transistor 214 and the emitter of transistor 215.Resistor 218 goes from the emitter of transistor 214 to the return pathand capacitor 210 goes from the collector of transistor 215 to thereturn path in parallel to resistor 218.

During the secondary voltage half wave interval when transformer 202point A is negative and no charging current flows, the point C of thetransformer 202 is positive in relation to tap point B. This half wavepositive potential supplies base drive to transistor 214.

The collector current of transistor 214 is the base current oftransistor 215. The collector current of transistor 215 chargescapacitor 220 to the battery voltage minus the saturation voltage oftransistor 215. Thus, the capacitor 220 voltage is an image of thebattery voltage during the intervals between charging current pulses.

CHARGE MEASUREMENT AND MEMORY CIRCUIT The charge measurement and memorycircuit consists of current transformer 221, diode 223, resistor 225,capacitor 227. All of these are in series. The primary winding ofcurrent transformer 221 is in series with the main charge currentcircuits. The secondary winding of transformer 221 is a faithfulreproduction of the primary current at a ratio determined by the currenttransformer. Resistor 225 limits this current and the current is storedin memory capacitor 227. The capacitor 227 voltage is a direct result ofthe charging current ampere-second-area." Diode 223 prevents capacitor227 from discharging in between battery charging pulses. The controlcircuit is based on a control SCR 222 in parallel with the battery undercharge. This control circuit, in addition to SCR 222 has diodes 224,226, SCR control resistor 228 in parallel with coil 230, NPN transistors232, 234, 236, reed relay switch 238 and switch load resistor 240. Thecontrol electrode of SCR 222 is controlled by diodes 242, 244 andresistors 246, 248. SCR 222 is in parallel with the battery and fed inseries at the base by diodes 224 and 226 while the control electrode iscontrolled by diodes 242, 244 and resistor 248 series and resistor 246in parallel with resistor 248. The diodes 242 and 244 in turn areconnected to the center top of variable resistor 250 in parallel withcapacitor 220 and connected to the control electrode of transistor 215.Firing is provided 'by resistor 252, diode 254 and parallel loadresistor 256. Bias is provided by resistors 260, 262.

Assume a discharged two-cell nickel-cadmium battery a is connected perFIG. 6. Upon energizing the primary, and during the positive half waveinterval, the gate of SCR 206 is fired through resistor 252 and diode254. Charging current then flows through SCR 206 and into battery 20a.During each negative half wave interval the battery is interrogated andits voltage is recorded on measuring capacitor 220. This sequencecontinues until the battery 20a is charged to the 90 percent point.During this charge time control SCR 222 is never turned on and diodes224 and 226, as well as transistors 232, 234 and 236 remain off.

The 90 percent point is determined from the voltage characteristics ofthe battery under charge. The control electrode of SCR 222 is fired whenthis voltage point is reached. The charger voltage reference consists ofdiodes 242 and 244 and the gate voltage of SCR 222. When the 90 percentpoint is reached, the circuit through SCR 222 is completed. Thisaccomplishes two distinct functions: (1 energizes reed relay coil 230and (2) completes the emitter current path for transistor 232. At thissame point in time, the reed relay closes completing a discharge pathfor the current stored in memory capacitor 228. The capacitor dischargecurrent through resistor 226 is the base current for transistor 236.

The collector current of transistor 236 is the base current oftransistor 234, when transistor 234 turns on,

transistor 232 is biased off. Transistor 232 remains off for theduration of capacitor 228 discharge time. The discharge time ofcapacitor 228 is a function of the value of resistor 226 and the valueof capacitor 228 and the voltage to which capacitor 228 was charged.

The voltage drop across resistor 228 is determined by its resistance andthe combined currents of parallel circuits consisting of resistor 252,diode 254 and resistor 256, while SCR 222 is biased off, the voltage atpoint D junction is great enough to trigger SCR 206 into conduction.After the discharge time of capacitor 228, transistor 236 turns off,transistor 234 turns off, and transistor 232 turns on. When transistor232 turns on, this completes a current path through resistor 256,transistor 232 and SCR 222 to ground. This lowers the voltage atjunctionE, allowing a greater current to flow through the circuit with resistor252, diode 254, resistor 228 and SCR 222. The added current throughresistor 252 and diode 254 causes a lower voltage to appear at point D.This low voltage at point D is not great enough to fire SCR 206 and thecharge cycle stops.

It is to be observed therefore that the present invention provides for abattery charger which contains the following advantages over othercommon charges:

(1) Fast recharge, typically 15 minutes for a 1,200 maH battery, (2)complete percent recharge, (3) no discharge path in battery circuit whenAC line is turned off, (4) simplicity because of few components, (5)reliability, and (6) low cost.

I claim:

1. In a battery charging device having:

a. a transformer for transforming an AC power line supply into usuableenergy including an SCR in series with said transformer for charging abattery and a current limiting resistor in series with said SCR and saidtransformer, said SCR including a control electrode;

b. a pulsating charging circuit operatively coupled to said transformer,SCR and current limiting resistor and disposed for charging a batteryacross a charging terminal (18) supplying a pulsating charging currentduring each half cycle of AC alternation;

c. a diode (39) connected to said SCR control electrode, a gatingtransistor (38) including an emitter connected to said diode and, acontrol transistor (40) with one electrode connected to said gatingtransistor base;

(1. sensing circuit means connected to said charging terminal forsensing the voltage charged in said battery during the non-chargingone-half cycle;

e. a measurement and memory circuit connected to said charging cirucitand said sensing circuit means including storage means for storing acharge therein which is a function of said battery charge;

f. a trickle charge circuit in parallel with said SCR, connected to saidcharging terminal (18), having a diode (50) and resistor (52) in series,

g. control means responsive to said voltage sensing means and coupled tosaid charging circuit for changing the duration of charge upon apredetermined battery voltage for a time period measured by saidmeasurement and memory circuit, the improvement therein comprising: h. asecond secondary (58), an internal power supply (22) connected to saidsecond secondary (58) including first and second power diodes (60, 64)in series with said second secondary (58) in parallel with each other ina back-to-back relationship, one of said diodes being connected to thecollector electrode of said gating transistor (38) providing half waverectification to control the firing of said transistor, a tap on saidsecond secondary, a power diode (62) in parallel with power biasresistors (68, 70).connected to said tap providing rectification of thesecond half wave, and voltage reference diodes (46, 47, 48, 49) inseries with said power diode (62) said power bias resistors (68, 70),the emitter of said control transistor (40) being connected to saidvoltage reference diodes; and,

. said sensing circuit means being voltage sensing means and including aresistor bridge (80, 82, 84, 86, 88) connected to said terminal (18), avoltage sensing transistor (92) operatively coupled to said bridge, anamplifier (A) connected to said bridge, an inverter (B) connected tosaid amplifier (A) inverting said amplifier output, a second amplifier(F) connected to said power section connected to said inverter (B)supplying charging information thereto, and, a disable means (c)connected to said inverter (B) and second amplifier (F) to disable thecharge measuring and terminate the main charge.

2. A device as claimed in claim 1, including a charge measurementcircuit connected to said disable means (C) including a first transistor(108) biased by said disable means (C), a second transistor (110) andrate limiting resistor (116) connected to be turned on by said firsttransistor (108) and a memory capacitor (122) connected to said secondtransistor (110) and charged thereby to a value which is a function ofthe battery charge.

3. A battery charger as claimed in claim 2, including an overchargeinterval circuit (28) for storing in a memory the time required to bringthe battery up to 90 percent of its full charge, said overchargeinterval circuit including, an amplifier (D) connected to the voltagesensing means (92), said disable means (C), and an overcharge transistor(124), a differential amplifier (126) connected to the collectorelectrode of said overcharge transistor including a plurality of inputresistors (128, 130) in parallel to the plus input of said differentialamplifier and a resistor (132) connected to the minus input thereof, anoutput differential amplifier resistor (134) connected between thedifferential amplifier and the base of said control transistor (40),said input resistors being connected to one and the other side of saidmemory capacitor.

4. in a battery charging device comprising in combination:

a. a transformer for transforming an AC power line supply into usuableenergy, including a current limiting resistor (204) and an SCR (206) inseries with said transformer and current limiting resistor for chargingsaid battery;

b. a pulsating charging circuit operatively coupled to said transformerand disposed for charging a battery across a charging terminal (18a)supplying a pulsating charging current during each half cycle of ACalternation;

c. sensing circuit means connected to said charging terminal for sensingthe voltage charged in said battery during the non charging r cycle;

d. a measurement an memory circuit means including storage means forstoring a charge therein which is a function of said battery charge;and,

e. control means responsive to said voltage sensing means and coupled tosaid charging circuit for changing the duration of charge upon apredetermined battery voltage for a time period measured by saidmeasurement and memory circuit, the improvement therein comprising:

f. a tap (13) on said transormer, a first NPN transistor (214) connectedto said tap at its base, a second NPN transistor (215) whose base isconnected to the collector of the first N PN transistor, a measurementcapacitor (22)0 charged by said second transistor collector to a valuecorresponding to said battery charge, said measurement capacitor (22)0sewing to interrogate the battery and record the battery voltagethereon;

g. a current transformer (222) fed by said transformer, a diode (223),resistor (225), and memory capacitor (227) in series with said currenttransformer secondary, said capacitor (227) memorizing the charge onsaid battery; and,

h. a control SCR (222) operatively connected between said measurementcapacitor (220) and said memory capacitor (227) by a switch (238), saidswitch (238) connected to said memory capacitor (227) acting to firesaid control SCR (222), whereby said measurement capacitor chargeincreases with charging time so that when said battery charge reachesabout percent of the full charge said measurement capacitor dischargesat a predetermined rate and causes the charging device to turn off whenabout 1 10 percent of the energy is restored to the battery undercharge.

UNITED STATES PATENT OFFICE Certificate Patent No. 3,733,53 i PatentedMay 15, 197 3 Seymour Saslow Application having been made by SeymourSaslow, the inventor named in the patent above identified, and EspeyManufacturing and Electronics Corporation, Saratoga Springs, N.Y., acorporation of the United States, the assignee, for the issuance of acertificate under the provisions of Title 35, Section 256, of the UnitedStates Code, adding the names of Robert Lackey and Charles R. Brandovvas joint inventors, and a showing and proof of facts satisfying the therequirements of the said section having been sub mitted, it is this 18thday of December 197 3, certified that the names of the said RobertLackey and Charles R. Brandow are hereby added to the said patent asjoint inventors With the said Seymour Saslow.

FRED W. SHERLING Associate Solicitor.

i in

UNITED STATES PATENT OFFICE Certificate Patent No. 3,7 33,534 PatentedMay 15, 1973 Seymour Saslow Application having been made by SeymourSaslow, the inventor named in the patent above identified, and EspeyManufacturing and Electronics Corporation, Saratoga Springs, N.Y., acorporation of the United States, the assignee, for the issuance of acertificate under the provisions of Title 35, Section 256, of the UnitedStates Code, adding the names of Robert Lackey and Charles R. Brandovvas joint inventors, and a showing and proof of facts satisfying the therequirements of the said section having been submitted, it is this 18thday of December 1973, certified that the names of the said Robert Lackeyand Charles R. Brandow are hereby added to the said patent as jointinventors with the said Seymour Saslow.

FRED W. SHERLING Associate Solicitor.

1. In a battery charging device having: a. a transformer fortransforming an AC power line supply into usuable energy including anSCR in series with said transformer for charging a battery and a currentlimiting resistor in series with said SCR and said transformer, said SCRincluding a control electrode; b. a pulsating charging circuitoperatively coupled to said transformer, SCR and current limitingresistor and disposed for charging a battery across a charging terminal(18) supplying a pulsating charging current during each half cycle of ACalternation; c. a diode (39) connected to said SCR control electrode, agating transistor (38) including an emitter connected to said diode and,a control transistor (40) with one electrode connected to said gatingtransistor base; d. sensing circuit means connected to said chargingterminal for sensing the voltage charged in said battery during thenonchargiNg one-half cycle; e. a measurement and memory circuitconnected to said charging cirucit and said sensing circuit meansincluding storage means for storing a charge therein which is a functionof said battery charge; f. a trickle charge circuit in parallel withsaid SCR, connected to said charging terminal (18), having a diode (50)and resistor (52) in series, g. control means responsive to said voltagesensing means and coupled to said charging circuit for changing theduration of charge upon a predetermined battery voltage for a timeperiod measured by said measurement and memory circuit, the improvementtherein comprising: h. a second secondary (58), an internal power supply(22) connected to said second secondary (58) including first and secondpower diodes (60, 64) in series with said second secondary (58) inparallel with each other in a back-to-back relationship, one of saiddiodes being connected to the collector electrode of said gatingtransistor (38) providing half wave rectification to control the firingof said transistor, a tap on said second secondary, a power diode (62)in parallel with power bias resistors (68, 70) connected to said tapproviding rectification of the second half wave, and voltage referencediodes (46, 47, 48, 49) in series with said power diode (62) said powerbias resistors (68, 70), the emitter of said control transistor (40)being connected to said voltage reference diodes; and, i. said sensingcircuit means being voltage sensing means and including a resistorbridge (80, 82, 84, 86, 88) connected to said terminal (18), a voltagesensing transistor (92) operatively coupled to said bridge, an amplifier(A) connected to said bridge, an inverter (B) connected to saidamplifier (A) inverting said amplifier output, a second amplifier (F)connected to said power section connected to said inverter (B) supplyingcharging information thereto, and, a disable means (c) connected to saidinverter (B) and second amplifier (F) to disable the charge measuringand terminate the main charge.
 2. A device as claimed in claim 1,including a charge measurement circuit connected to said disable means(C) including a first transistor (108) biased by said disable means (C),a second transistor (110) and rate limiting resistor (116) connected tobe turned on by said first transistor (108) and a memory capacitor (122)connected to said second transistor (110) and charged thereby to a valuewhich is a function of the battery charge.
 3. A battery charger asclaimed in claim 2, including an overcharge interval circuit (28) forstoring in a memory the time required to bring the battery up to 90percent of its full charge, said overcharge interval circuit including,an amplifier (D) connected to the voltage sensing means (92), saiddisable means (C), and an overcharge transistor (124), a differentialamplifier (126) connected to the collector electrode of said overchargetransistor including a plurality of input resistors (128, 130) inparallel to the plus input of said differential amplifier and a resistor(132) connected to the minus input thereof, an output differentialamplifier resistor (134) connected between the differential amplifierand the base of said control transistor (40), said input resistors beingconnected to one and the other side of said memory capacitor.
 4. In abattery charging device comprising in combination: a. a transformer fortransforming an AC power line supply into usuable energy, including acurrent limiting resistor (204) and an SCR (206) in series with saidtransformer and current limiting resistor for charging said battery; b.a pulsating charging circuit operatively coupled to said transformer anddisposed for charging a battery across a charging terminal (18a)supplying a pulsating charging current during each half cycle of ACalternation; c. sensing circuit means connected to said chargingterminal for sensing the voltage charged in said battery duRing the noncharging 1/2 cycle; d. a measurement an memory circuit means includingstorage means for storing a charge therein which is a function of saidbattery charge; and, e. control means responsive to said voltage sensingmeans and coupled to said charging circuit for changing the duration ofcharge upon a predetermined battery voltage for a time period measuredby said measurement and memory circuit, the improvement thereincomprising: f. a tap (13) on said transormer, a first NPN transistor(214) connected to said tap at its base, a second NPN transistor (215)whose base is connected to the collector of the first NPN transistor, ameasurement capacitor (22)0 charged by said second transistor collectorto a value corresponding to said battery charge, said measurementcapacitor (22)0 serving to interrogate the battery and record thebattery voltage thereon; g. a current transformer (222) fed by saidtransformer, a diode (223), resistor (225), and memory capacitor (227)in series with said current transformer secondary, said capacitor (227)memorizing the charge on said battery; and, h. a control SCR (222)operatively connected between said measurement capacitor (220) and saidmemory capacitor (227) by a switch (238), said switch (238) connected tosaid memory capacitor (227) acting to fire said control SCR (222),whereby said measurement capacitor charge increases with charging timeso that when said battery charge reaches about 90 percent of the fullcharge said measurement capacitor discharges at a predetermined rate andcauses the charging device to turn off when about 110 percent of theenergy is restored to the battery under charge.